The present invention relates to a ferroelectric liquid crystal touch panel.
In recent years, accompanying the increase in the amount and complication of information treated in information devices, there is the related tendency that various devices are becoming too large and complicated. Therefore, in order to make the entire device compact, a device has been proposed which has both an input function and another function, such as a display function.
For example, a device provided with such plural functions is a panel using a liquid crystal as will more specifically be shown hereinafter.
A first such device includes a liquid crystal panel equipped with an input function and which determines the change of distance between electrodes of the panel in the case when the display surface of the liquid crystal panel is pushed as a change of the electrical capacity, and the pushed position of the liquid crystal panel is detected thereby.
The second such device includes a liquid crystal panel equipped with an input function and which effects heat writing with a light pen comprising a semiconductor laser and a focussing lens into the liquid crystal display device using a thermoelectric optical effect. The difference of the display state is determined as a change of the electric capacity, and the position thermally written on the liquid crystal panel is detected thereby.
In the above-described first liquid crystal panel, since the liquid crystal shows dielectric constant anisotopy, the electric capacity changes also by the display state of the liquid crystal (on, off, or intermediate state). It is therefore necessary to separate the change of electric capacity in the case when the display surface of the panel is pushed and there is a change of electric capacity due to the display state. Therefore, the construction of the detecting circuit becomes complicated, and together with that, there is the problem that separation of the above-described respective capacities becomes extremely difficult.
In the above-described second liquid crystal panel, since the change of the writing-in state is detected as a change of electric capacity, there is the problem that the input cannot be effected without changing the display state. Further, since a special device such as a light pen and the like is required, there is also the problem that the device becomes expensive.
As described above, it was impossible heretofore to obtain an effective liquid crystal panel equipped with both an input function and another function, such as a display function.
An object of the present invention is to obtain a liquid crystal panel equipped with a plural number of functions, including an input function.
The present invention utilizes the piezoelectric effect of a ferroelectric liquid crystal.